Method of making brake-shoes.



UN ITEo STATES PATENT OFFIcE.

JAMES TIMMS AND SAMUEL PRESCOTT BUSH, OF COLUMBUS, OHIO, AS-

SIGNORS TO THE BUCKEYE MALLEABLE IRON AND COUPLER 00., OF

COLUMBUS, OHIO.

METHOD OF MAKING BRAKE-SHOES.

SPECIFICATION forming part of Letters Patent No. 721,845, dated March 3, 1903. Application filed October 3,1901. Serial No. 77,476. (No model.)

To all whom it may concern:

county of Franklin and State of Ohio, have invented certain new and useful Improvements in Methods of Making Brake-Shoes; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

Our invention relates to an improved method of making brake-shoes, the object of the invention being to provide an-improved method of this character which will produce a brake-shoe of great strength and wearing qualities and at the same time present just the proper friction against the wheel to perform the best results.

With this object in View the invention consists in certain novel steps in the method, as will be more fully hereinafter described, and pointed out in the claims.

Heretofore in the manufacture of brakeshoes the entire shoe (or where inserts are employed the greater portion of the shoe) is cast, which casting being usually of gray iron is granular and necessarily more or less brittle and breaks or cracks after the shoe has become partially worn, and to avoid this defect our invention was devised.

With our improved method in constructing a shoe without inserts we first cast the shoe by pouring into a mold chilling mixture of iron in molten condition. This chilling mixture of iron is one that when poured into a mold will chill in such a way that the carbon in the iron is largely thrown into a combined state with the iron, making a very hard metal with a white fracture calledwhite or chilled metal. We then subject the shoe to an annealing process or heating treatment for a sufficient length of time to partly decarbonize the hard-chilled metal or to change the state of the carbon from that of combined to graphitic carbon, and thus change it from a brittle condition to a ductile condition. Af-

ter this heating the shoeis cooled, when the metal will have become comparatively soft. The shoe is again subjected to a red heat of greater or less degree in an ordinary furnace and then removed and cooled in the open air. The greater the degree of reheating the greater will be the degree of hardness obtained. The object of the first heating treatment or annealing process is to insure getting the necessary degree of softness and ductility, and of the reheating process to more exactly graduate the degree of hardness which it is finally desired to obtain in order to produce the required degree of friction and durability.

We have found that after the steps of reheating and-subsequent cooling in the atmosphere the grain of the iron is made a great deal more compact, and a certain proportion of the carbon, which in the process of annealing has been changed from the combined to the graphite carbon, is again thrown back into the combined state. The reason for this treatment is that the exact hardness or texture can be better controlled by this process than by a direct process of annealing. The result is a material well adapted to brake-shoe service, providing the necessary friction and at the same time making the shoe strong and tough enough to be worn down thin.

When it is desired to construct acompositefaced shoe, or, in other Words, a shoe whose wearing face is composed of two metals of different degrees of hardness, the inserts are first placed in the mold and the body of the shoe cast around the same. The shoe is then heated and reheated practically as above explained to produce a hard and ductile shoe and at the same time present a wearing face of two metals of difierent degrees of hardness in which the metals will be practically integral.

Where theiuserts are applied, the ordinary cast brake-shoe is apt to break at some point where one of these inserts is applied. With our process the inserts can be worn completely out without any danger of the shoe breaking, and thus we can obtain all the benefits of the composite brakeshoe so far as braking power and durability are concerned and yet have it free from the danger of breaklng.

Having fully described our invention, What we claim as new, and desire to secure by Letters Patent, is

1. An improved method of making brakeshoes, consisting of casting the shoe of chilling iron into proper shape and then annealing it, then reheating and subsequently cooling, it.

2. An improved method of making brakeshoes, consisting of casting the shoe of chilling iron into proper shape then annealing it by heat and after cooling the shoe subjecting it to a reheating process, and finally cooling it in the atmosphere.

3. An improved method of making brakeshoes, consisting of casting the body of the shoe of chillingiron around inserts placed in JAMES TIMMS. SAMUEL PRESCOTT BUSH.

Witnesses:

H. N. SMITH, JOSEPH STAFFORD. 

